#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <bitset>
#include <utility>
using namespace std;

#define mm(a, n) memset(a, n, sizeof a)
#define mk(a, b) make_pair(a, b)

const double eps = 1e-6;
const int INF = 0x3f3f3f3f;

typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;

inline void quickread()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
}
int dp[1005];
int v[105], w[105];

inline void solution()
{
    int n, m;
    int i;
    cin >> n >> m;
    for (i = 1; i <= m; i++)
        cin >> w[i] >> v[i];
    mm(dp, 0);
    for (i = 1; i <= m; i++)
        for (int j = n; j >= w[i]; j--)
            dp[j] = max(dp[j], dp[j - w[i]] + v[i]);
    cout << dp[n] << endl;
}

int main()
{
    // freopen("input.txt", "r", stdin);
    quickread();
    solution();
    return 0;
}